There are may different kinds of television video signals, the format of which varies from country to country. In the United States and Japan, for example, the NTSC format is used. NTSC stands for National Television Systems Committee, which is the name of the organization that developed the standard. In Europe, the PAL format is common. PAL stands for phase alternating line. SECAM is a standard used in France and stands for sequential colour avec memoire (sequential color with memory). It should be noted that there are about 15 different sub-formats contained within these three general formats. Each of these formats is not generally compatible with the others. Although they all utilize the same basic scanning system and represent color with a type of phase modulation, they differ in specific scanning frequencies, number of scan lines, and color modulation techniques.
For whatever type of television video standard employed, there are three basic levels of baseband video signal interfaces. In order of increasing quality, they are composite (or CVBS), which uses one wire pair; Y/C (or S-video), which uses two wire pairs; and component, which uses three wire pairs. Each wire pair consists of a signal and ground wire. These three interfaces differ in their level of information combination (or encoding). More encoding typically degrades the quality but allows the signal to be carried on fewer wires. Component signals have the least amount of encoding and composite signals the most.
Composite signals are the most commonly used analog video interface. Composite video is also referred to as CVBS, which stands for color, video, blanking, and sync, or composite video baseband signal. It combines the brightness information (luma), the color information (chroma), and the synchronized signals on just one cable.
The Y/C signal, often referred to as “S-video,” is a less encoded video signal. Brightness (luma), which is the Y signal, and the color (chroma), the C signal, are carried on two separate sets of wires.
Component signal interfaces are the highest performance, because they have the least encoding. The signals exist in nearly native format. They always utilize three pairs of wires that are typically in either a luma (Y) and two-color difference-signals format or a red, green, blue (RGB) format. RGB formats are almost always used in computer applications, whereas color-difference formats are generally used in television applications. The Y signal contains the brightness (luma) and synchronizeing information, and the color-difference signals contain the red (R) minus the Y signal and the blue (B) minus the Y signal. The theory behind this combination is that each the base R, G, and B components can be derived from these difference signals. Common variations of these signals are as follows:                (1) Y, B-Y, R-Y: Luma and color-difference signals.        (2) Y, Pr, Pb: Pr and Pb are scaled versions of B-Y and R-Y.        (3) Y, Cr, Cb: Digital signal equivalent to Y, Pr, Pb.        (4) Y, U, V: intermediate quadrature signals used in the formation of composite and Y/C signals.        
Audio stereo signal standards for television broadcasts include MTS, standing for Multichannel Television Sound also know at the BTSC standard. This is one of the first developed stereo sound systems. BTSC is used in conjunction with NTSC/525, mainly in North America and parts of South America. BTSC, or MTS, comprises two, and sometimes three separate signals for transmitting stereo audio. The first signal is formed as the sum of the left and right audio signals, and can be detected by both monophonic television receivers (to preserve compatibility with such receivers) and stereo receivers. The second signal is formed as the difference between the left and right audio signals, and is detectable only by stereo receivers. In many cases, a third signal, the Secondary Audio Program (SAP), provides for a second language or a descriptive commentary for the blind.
The FM-FM standard is used in Germany, Austria, Holland, Switzerland and Australia. This standard uses a twin channel to transmit analog FM stereo transmissions. Like BTSC, the secondary channel can be used to transmit a second language. NICAM, stands for Near Instantaneously Companded Audio Multiplex NICAM, officially called NICAM 728 and is used throughout Europe and Asia. NICAM is a digital two-channel audio transmission system with a sub-code selection of bilingual operation. Because it is digital, playback is that of near Compact Disc quality. EIAJ, standing for the Electronics Industry Association of Japan, was developed and is used in Japan. EIAJ systems use a subcarrier within the main FM audio carrier. The subcarrier is an FM subcarrier rather than the suppressed AM subcarrier used in the BTSC system or in FM radio broadcasting. Zweiton is a digital stereo standard that was developed out of A2 German Stereo and is used throughout Europe and Asia. Like the other systems, Zweiton has a main carrier signal and a secondary carrier signal usually used for the audio of a second language.
The television broadcast systems and standards described generally have employed analog and mixed analog-digital architectures to place the input audio and video signals onto intermediate (IF) frequencies. The use of IF frequencies and analog architectures has presented problems for use in digital television applications, including the requirement for intricate and costly filter topologies.